Key Information

Vocabulary: Nutrition

Nutrition

Getting the matter and the energy that every living being needs to grow, survive and reproduce. As it also involves the removal of waste substances and residual energy, it can be described as an exchange of matter and energy with the environment.

Breathing

The movements performed by the lungs (along with the rib cage) to inhale and exhale the atmospheric air.

Respiration

The process carried by the mitochondria, whereby small energetic nutrients (monosaccharides, fatty acids) are burnt with the help of the oxygen to produce the energy that the cells need. This process also involves the removal of CO2, H2O(g), and heat.

Gas exchange

You need to convey O2 from the atmospheric air to the mitochondria and to convey the CO2 produced in the mitochondria to the atmospheric air. To do this, two gas exchanges are needed: (a) between the alveoli and the blood and (b) between the blood and the cells of every organ in your body. The blood vessels that take part in both gas exchanges are always the capillaries, because of their very thin membranes.

Blood

The fluid that, amongst other things, conveys (a) the oxygen from the lungs to the cells, (b) the other nutrients from the small intestine to the cells, (c) the CO2 from the cells to the lungs, and (d) the other waste substances from the cells to the kidneys and the sweat glands.

Heart

The organ that pumps the blood throughout all the body. It has two chambers to receive the blood (right and left atria) and two others to expell the blood (the left and right ventricles). Two valves (tricuspid and mitral) control the passing of the blood from the atria to the ventricles, and two other valves (aortic and pulmonary) control the passing of the blood from the ventricles to the arteries.

Blood vessels

The organs that transport the blood throughout all the body. The arteries transport the blood from the heart to the organs (small arteries are called arterioles), the veins from the organs to the heart (small veins are called venules), and the capillaries are the very thin ones that perform the exchange of gases between the blood and the cells or the blood and the alveoli.

Excretion

Disposing of the waste substances produced by the cells. It is done through the exhalation movement of the lungs, the kidneys and the sweat glands.

Vocabulary: Digestive System

Peristalsis

The wavelike muscular contractions of the digestive tract by which its contents are forced to move onwards. It is performed by the ring-like muscles of the walls of the esophagus, the stomach and the intestines.

Bolus

The food mass that crosses the esophagus after having undergone a first digestive stage in the mouth.

Chyme

The fluid food mass that is produced in the stomach when the bolus undergoes a second digestive stage.

Chyle

The very fluid food mass that is produced in the duodenum when the chyme undergoes the third digestive stage.

Enzymes

They are special proteins that behave as catalysts, i.e., they accelerate each and every chemical reaction in your body; otherwise, those chemical reactions wouldn't take place, or would do at a very slow pace. Enzymes are very specific and each one can catalise only one chemical reaction: for instance, the only thing that salivary amylase can do is breaking the starch into maltose.

Digestive enzymes

The enzymes that break down the long molecules in the foods into much smaller ones that can later on be absorbed into the bloodstream. The main ones are the amylases (break down carbohydrates into sugars), the proteases (break down proteins into aminoacids) and the lipases (break down the lipids into glycerol and fatty acids). They come in the following digestive juices: the saliva, the gastric juice, the pancreatic juice and the intestinal juice.

Bile

One of the five digestive juices. It is produced by the liver, stored in the gall-bladder, and it is greenish. It is necessary mostly not to carry digestive enzymes to the duodenum, but to transport bile salts to the duodenum. The bile salts are necessary to help the lipids to "dissolve" in the chyle, forming small droplets, easy to be attacked by the lipases. This process is called emulsification.

Villi

The finger-like folds in the small intestine. They increase greatly the absorption surface in the small intestine (otherwise, the absorption of the nutrients from every meal would last for weeks). To allow an easy passing of the nutrients, they are very thin. Inside them, the nutrients are collected by capillary vessels and lymphatic vessels, and end up in the bloodstream.

pH

A measurement that expresses the level of acidity of a substance: the lower the pH, the greater the acidity; the higher the pH, the greater the alkalinity. Substances with a pH of 7 are neutral, i. e., neither acid nor alkaline.

Lymph

A clear fluid that circulates through the vessels of the lymphatic system. It collects the lipids in the small intestine and transports them to the bloodstream near the neck; it also helps the maturing of the young white blood cells before they are sent to the blood.

Functions of the Digestive System

What

Where

Digestion

Breaking down the foods into small molecules that the blood can absorb later on (the nutrients) and into somewhat bigger molecules that can't be absorbed (dietetic fibre and others).

Mouth, stomach and duodenum

Absorption

The small nutrients from the digested foods pass from the digestive tract to the blood and the lymph.

Jejunum and ileum

Elimination

The indigestible molecules of the foods and some other waste substances are expelled out of the body.

Rectum and anus

Digestive Juices

Produced by

Released to

Saliva

Salivary glands (parotids, sublinguals and submandibulars).

Mouth

Gastric juice

Small glands in the lining of the stomach.

Stomach

Bile

Liver (and stored in the gall-bladder).

Duodenum

Pancreatic juice

Pancreas.

Duodenum

Intestinal juice

Small glands in the lining of the duodenum.

Duodenum

Mind Map: Food additives

External Links

Digestive System

The digestive system at Web-books.com.A good overview, with text and images, on all the organs of the digestive system and their work. The left menu contains a link to a wide series of digestive diseases.

The digestive system at Faqs.org.Another wide overview, with text and images, on all the organs of the digestive system and their work, the digestive diseases, a glossary and additional readings.

The digestive system.To dig deeper, visit this website with lots of info and images on the digestive system.

We are more microbe than man.About a 90% of your cells are not yours: they are bacteria, most of which live in your intestines. Learn why. You can also listen to the embedded audio version of the article.

Why does my stomach growl?Whether you call it grumbling, rumbling, gurgling or growling, from time to time everybody's belly chimes in. Learn why.

The respiratory system at Web-books.com.A good overview, with text and images, on all the organs of the respiratory system and their work. The left menu contains a link to a wide series of respiratory diseases.

The respiratory system at Faqs.org.Another wide overview, with text and images, on all the organs of the respiratory system and their functions, the respiratory disorders, a glossary and additional readings.

Circulatory System

The cardiovascular system at Web-books.com.A good overview, with text and images, on all the organs of the circulatory system and their work. The left menu contains a link to a wide series of cardiovascular diseases.

The blood at Web-books.com.A good overview on the blood, its cells and their work. The left menu contains a link to a wide series of blood diseases.

The cardiovascular system at Faqs.org.Another wide overview, with text and images, on all the organs of the circulatory system and their work, the blood, the cardiovascular disorders, a glossary and additional readings.

How blood works.Detailed description of the composition and the function of the human blood. It contains two animations that start on page load… you might want to stop and restart them after reading the texts.

Nutrients, Diets and Foods

How food works.A lot of interesting and detailed info about the main human nutrients. It contains some images and one animation that starts on page load… you might want to stop and restart it after reading the texts.

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